28 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 
larger tlian the second, both similar to the aual; pectoral fins short, 
obtuse, or truncate ; color gray. L. 4 to 0 feet. 
A small voracious sliark with very shari) teeth, rather common on 
our Atlantic coast. 
(Si/uahis americantiH Mitch. Trans. Lit. & Phil. Soc. 181‘!, i, 488: Sqiialus littoralis 
Mitch. Am. Monthly Ma<>'. ii, 1818, liCB: rarc/zar/ri.s Storcr, Fi.shes Mas.s. 217: 
Odoniaspls americ(i)iiis Giintlier, viii. :{l)2 : EitqomphodiiH littondin Gill, Proc. Ac. Nat. 
Sci. Phila. ISlH, 2(i0.) 
Family XL— LAMNID^. 
{The Po )•])€(( glefi.) 
Sharks of large size, with the body stout, the mouth wide, with large 
teeth, aud the caudal fiu lunate, the two lobes being not very unequal, 
the u])per lobe strongly bent upward 5 caudal i)eduncle with a keel on 
each side; gill-openings wide, all in front of the pectorals, entirely lat- 
eral, not extending under the throat ; first dorsal large ; i»ectorals large ; 
ventrals moderate; second dorsal and anal very small; a. pit at the root 
of the caudal; spiracles minute or absent. Genera 3; species (J or 
more. Those inhabiting our coasts have been much confused by authors. 
{Lamni(}a\ part, (Tilnther, viii, 389-392.) 
* Teeth 'with entire cdgccs. 
d. Teeth without hasal cusps, long, Ilexnons, in-isuiatie, and acute.. -IsURUS, 26. 
ua. Teeth, or ino.st of them, with a small cusp on each side at base. compi’e.ssed, 
sharp, and somewhat triangular Lamxa, 27. 
** Teeth with .seirated edg(‘s, eompressed, and triangular iu form . . C.vRCliAltODOX, 28. 
26.— ISUKUS Ralinescpie, 1810. 
Porbeagles. 
{(Xryrhlna Ag. ) 
(Rafinesque, Caratteri di Alcuni Nuovi Generi : type Jmnis oxiirhi/nchus Raf.=Ox(/r7ii//a 
fi 2 )(tU(insaiiii Bon.) 
Snout rather long and pointed ; lirst dorsal and ])ectorals large ; sec- 
ond dorsal and anal very small; (jandal peduncle slender; teeth long, 
lanceolate, with sliarj* entire cutting edges and no basal cusps. 
etpial; dupd, tail; the two lobes of the tail being nearl}’ equal, as in all 
the members of this family.) 
* First dorsal inserted (mtirely behind ])ectorals, nearly midway l)etween pectorals and 
ventrals. {Tsiiropnis Gill.) 
3 . 5 . I. giniietlS (M. A. H.) .Jor. A Gilb . — Mackerel Shark. 
This species, if really occurring on our coast, will be known from tlie 
other Puri by the position of the dorsal, which is distinctly behind the 
